cheap meter or measuring device for solar energy from panels.

edurbrowedurbrow Registered Users Posts: 5 ✭✭
edited January 29 in Solar Beginners Corner #1
Newbie here. I'm just getting started, got panels, charge controller and inverter from a friend who upgraded. I bought two 12v batteries. I don't have much money to spend.
What is the name of the device I need in order to measure the energy I'm collecting with solar panels? I'm still connecting panels and building frames for them and I want to see what effect placement, tilt and addition of panels make. Right now I have a Solar Charge Controller that is 30A PWM. It only has 3 lights on it. I see green when it is directly sunny and the red one lights up if it is not sunny enough or if I run the TV for a half hour. It is night now and I just checked the charge controller, the amber light is on along with the red one. I would like something more detailed than that, so I can see how the angle and tilt of the panels make a difference.

I have two more Solar Charge Controllers, but they are 10A MPPT and 15A. They both have displays, but I haven't tried them yet because I figure more amps are better. Is that right? I also want to track the voltage collected in the batteries. I have a multi-meter and I guess I could use that, but is there a simple gage or meter that could be attached permanently? I know there must be a range of prices from simple LED meters to complicated things that send data to computers. (Reading it on computer would be very convenient though!) What is a good starter for me, as a beginner with just 8 1/2 panels?
Also, what is a good meter to see the state of my 2 batteries? I can use my multi-meter, but something more permanent would be better, if it is cheap enough. My inverter makes a loud warning sound when I've just run the TV off the system for not very long. Any advice is much appreciated.
TIA
PS would a Kill A Watt meter work for Japan where the voltage is 100v?

Thank you in advance.

Comments

  • softdownsoftdown Solar Expert Posts: 3,479 ✭✭✭✭
    DC  clamp meter. Most only offer AC measuring. 
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • BB.BB. Super Moderators, Administrators Posts: 31,068 admin
    There are "tons" of DC power meters out there these days--And cheap:

    https://www.amazon.com/s?k=dc+power+meter&ref=nb_sb_noss

    Just be aware, if you connect one to a DC battery bank, it is not always clear how they will "behave". Some may log AH/WH as the batteries discharge, but may subtract as batteries recharge, or not show any change, or may continue to log a discharge... (each type has its place).

    The "true" Battery Monitoring Systems have this all worked out (including loss factors for batteries, etc.), but they do tend to be much more expensive vs the Amazon link (Ebay, others). This link is to our hoist Northern Arizona Wind & Sun:

    https://www.solar-electric.com/search/?q=battery+monitor

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 31,068 admin
    What Softdown recommended (DC Current Clamp DMMs) are great for debugging and understanding how your system works, but not for permanent installation/monitoring. Here are a couple of examples of DC+AC current clamp DMMs:

    https://www.amazon.com/gp/product/B0772FYF5M/ref=ox_sc_saved_title_1?smid=A3PUZ24ZTJP3C5&psc=1 (less expensive)
    https://www.amazon.com/gp/product/B019CY4FB4 (mid priced)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,365 ✭✭✭✭✭
    edurbrow said:
    I have two more Solar Charge Controllers, but they are 10A MPPT and 15A. They both have displays, but I haven't tried them yet because I figure more amps are better. Is that right? 
    I think there are a couple misconceptions.  This first is that solar panels produce amps. The charge controller amp rating is  the max it can handle generally on input with PWM...   

    The batteries, assuming lead acid, taper off the amount off amps they accept as they approach fully charged.

    I'd suggest a system shunt based battery monitor, like the Trimetric, but they aren't inexpensive.

    https://www.solar-electric.com/bogart-engineering-tm-2030-rv-battery-monitor.html

    ...an inexpensive PMW chrge controller with display, might give you more informtion  bout how much current(amps) is passing  through to the batteries.

    If you hunt round, you can find cheap PWM CC that will display amps ffor $40-50.  Thiss   onne   will   ddissply  current  system voltage  for $ll,  that might be enough if you are willing to learn the relation and cycling of voltage through out the  charging  cycle/day.

    https://www.amazon.com/Charge-Controller-Battery-Regulator-System/dp/B07T1X232K/ref=sr_1_7
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • littleharbor2littleharbor2 Solar Expert Posts: 1,557 ✭✭✭✭
    Victron is another

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • edurbrowedurbrow Registered Users Posts: 5 ✭✭
    BB. said:
    There are "tons" of DC power meters out there these days--And cheap:

    https://www.amazon.com/s?k=dc+power+meter&ref=nb_sb_noss
    Thank you Bill.
    Would this be a meter I could put between the panels and the charge controller? I think one review said that but the others were on the battery. It seems it can affect the output. I want to put it about 20 feet from where the charge controller is and see how the watts? voltage? amps? change as I add panels or change the angle or tilt.
  • edurbrowedurbrow Registered Users Posts: 5 ✭✭
    ...an inexpensive PMW chrge controller with display, might give you more informtion  bout how much current(amps) is passing  through to the batteries.
    Am I wrong in assuming that 30 amps is better than 10 or 15? With 60 watt panels, how many do I need before I have to worry about overloading? Right now, I don't understand anything. Could I try the 10 or 15 amp charge controller with no worries? What is the difference between them? Do more amps charge the batteries faster?


  • BB.BB. Super Moderators, Administrators Posts: 31,068 admin
    Regarding where to put the meter... Make sure that the meter is rated for the maximum voltage you expect from the array (i.e., Voc-array = 80 volts, then the meter should be rated >80 volts).

    Note that digital meters use electricity to make their readings/store values/etc.... Some may draw directly from the input power, others may have separate (or separately) DC point to the electronics (i.e., meter goes blank at night, forgets daily harvest, etc.--Or with separate power input from (example 24 volt battery bank), shows zero power/volts/current and saves current WH/AH harvest numbers). The meters probably draw almost zero Watts/Amps from DC power source (when compared to the 100s+ Watts from solar array).

    You can have issues... Many digital devices have common DC ground references (i.e., the negative wire from the solar array is "bonded" to the Negative DC remote power input--As an example). You can get into issues of "stray current flow" between the array negative and the battery bus negative... Just do your research. Isolated DC power input (vs measured load connections) are usually better (safer), but tend to be more expensive (to manufacture an onboard isolated power supply).

    Sorry to be so wordy--This can be a big issue, and I have never "played" with these devices before to know their ins and outs.

    REgarding is a 10 amp PWM controller not as good as a 30 Amp controller... To a degree, it is just cheaper (less copper, smaller transistors, etc.) to build a 10 amp controller vs a 30 amp controller. If you never plan on needing more than 10 amps, then a 30 amp controller (if more expensive) is not a great help. Note that electronics do age/fail with temperature... A 30 amp controller should be cooler than a 10 amp controller, when both carrying a 10 amp load. For this side of the argument, a larger controller running cooler should last longer (assuming both good quality controllers). Good ventilation (good cooling) is always important with power/electronics.

    Downside with larger controllers--May draw more energy to run the larger parts (PWM controllers typically do not draw that much power anyway--MPPT controllers use more power). So, a "too large" controller can waste energy on a smaller system.

    For 60 Watt panels, assume Vmp~18 volts:
    • 60 Watts / 18 volts Vmp = 3.33 Amps Imp per panel
    • 10 amp controller * 0.80 NEC solar derating = 8.0 Amps nominal max current
    • 8.0 amps derated controller / 3.33 amps = 2.4 panels ~ 2 panels (120 Watt array) maximum
    As always, read the charge controller manual. The 0.80x NEC derating, if the controller is rated for 10 amps, then you should be able to use 10 amps (in my humble opinion)--The NEC derating would seem to be a bit bogus (here). There are times when you can get more solar energy (clouds can "focus" extra sunlight/energy on array)... So, the derating is not totally bogus.

    And, I like to use the NEC 1.25 / 0.80 deratings for wiring/switching/circuit breakers/fuses/etc... For example, NEC type fuses/breakers are typically rated to blow at 1.0x or higher than rated current, and not blow at 0.80x rated current. So for a 15 amp branch circuit (wiring/breaker):
    • 15 amps * 0.80 derate = 12 amps maximum continuous rated current (suggested by me, NEC also uses for continuous current--Like Gym Lighting that runs 8+ hours per day)
    If you want to run 15 amps, then:
    • 15 amps * 1.25 NEC derating = 18.75 Amps ~ 20 amp rated wiring/breaker/fuse
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,365 ✭✭✭✭✭
    edurbrow said:
    ...an inexpensive PMW chrge controller with display, might give you more informtion  bout how much current(amps) is passing  through to the batteries.
    Am I wrong in assuming that 30 amps is better than 10 or 15? With 60 watt panels, how many do I need before I have to worry about overloading? Right now, I don't understand anything. Could I try the 10 or 15 amp charge controller with no worries? What is the difference between them? Do more amps charge the batteries faster?
    Some will display more info than others. Output will be determined by the solar panel. You will get no additional output from a 30 amp Charge controller than l0 amp unless you change the panels.

    Before it comes up, Charge controller charge batteries, if you have a lot of sun but your batteries are full, they will NOT send any more power to the battery bank.

    ...also lead acid batteries tapper off while approaching full, If you are comparing setups you should put a load on the system to be sure the charge controller is sending the max current.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
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